1. Field of the Invention
The present invention relates generally to methods and systems for drilling in various subsurface formations such as hydrocarbon containing formations.
2. Description of Related Art
Hydrocarbons obtained from subterranean formations are often used as energy resources, as feedstocks, and as consumer products. Concerns over depletion of available hydrocarbon resources and concerns over declining overall quality of produced hydrocarbons have led to development of processes for more efficient recovery, processing and/or use of available hydrocarbon resources.
In drilling operations, drilling personnel are commonly assigned various monitoring and control functions. For example, drilling personnel may control or monitor positions of drilling apparatus (such as a rotary drive or carriage drive), collect samples of drilling fluid, and monitor shakers. As another example, drilling personnel adjust the drilling system (“wiggle” a drill string) on a case-by-case basis to adjust or correct drilling rate, trajectory, or stability. A driller may control drilling parameters using joysticks, manual switches, or other manually operated devices, and monitor drilling conditions using gauges, meters, dials, fluid samples, or audible alarms. The need for manual control and monitoring may increase costs of drilling of a formation. In addition, some of the operations performed by the driller may be based on subtle cues from drilling apparatus (such as unexpected vibration of a drilling string). Because different drilling personnel have different experience, knowledge, skills, and instincts, drilling performance that relies on such manual procedures may not be repeatable from formation to formation or from rig to rig. In addition, some drilling operations (whether manual or automatic) may require that a drill bit be stopped or pulled off the bottom of the well, for example, when changing from a rotary drilling mode to a slide drilling mode. Suspension of drilling during such operations may reduce the overall rate of progress and efficiency of drilling.
Bottom hole assemblies in drilling systems often include instrumentation, such as Measurement While Drilling (MWD) tools. Data from the downhole instrumentation may be used to monitor and control drilling operations. Providing, operating, and maintaining such downhole measuring tools may substantially increase the cost of a drilling system. In addition, since data from downhole instrumentation must be transmitted to the surface (such as by mud pulsing or periodic electromagnetic transmissions), the downhole instrumentation may provide only limited “snapshots” at periodic intervals during the drilling process. For example, a driller may have to wait 20 or more seconds between updates from a MWD tool. During the gaps between updates, the information from the downhole instrumentation may become stale and lose its value for controlling drilling.